Joe Biden has just taken the lead in the key battleground state of Georgia.

The momentum surge of mail-in ballots for the Democrat threatens to extinguish President Trump's pathway to 270 electoral votes as the drama continues in the 2020 US election.

In what had been a razor thin margin all day, Biden continued to chip away at Trump's advantage and took the lead just after 10:30pm NZT.

For 40 hours, US President Donald Trump fumed in private and tweeted his grievances in all caps.

When he at last emerged, it was to stand behind the presidential seal in the White House and deliver a diatribe most notable for his litany of false statements about the election and his attempt to cast doubt on the integrity of the Democratic process.

As votes continued to be counted and Joe Biden edged closer to victory, Trump lashed out in a performance that suggested he knew his prospects for a second term were slipping away.

"If you count the legal votes, I easily win. If you count the illegal votes, they can try to steal the election from us," Trump claimed.

In fact, there is no evidence that any votes cast illegally are being counted or that the process is unfair and corrupt.

The ballot-counting process across the country largely has been running smoothly with no evidence of widespread fraud or problems.

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Trump delivered his statement before reporters in the White House briefing room and left without taking questions. It came after Trump and his allies spent a second day watching and waiting with the rest of the nation as vote totals pushed further in Biden's direction in some key battlegrounds.

With just a handful of states yet to be decided, Biden had a clear advantage over Trump, but the president still retained a narrow path to the 270 electoral votes needed to win reelection.

The Associated Press has not declared a winner, and it could take several more days for the vote count to conclude and a clear winner to emerge.

Reaction to the claims from an exhausted-looking Trump was swift.

MSBNC, NBC and ABC News all cut away from Trump's speech shortly after he started speaking.

MSNBC instead aired legal experts fact checking the President rather than his comments.

CNN and Fox News carried the full press conference. "What a sad night for the American people ... lie after lie after lie," said CNN's anchor immediately after Trump's speech.

Earlier Biden said he had ''no doubt" he will win the election and told his supporters to stay calm as votes continue to be counted.

Biden delivered brief remarks at a theatre in downtown Delaware.

He said it was "the will of the voters — no one, not anyone else — who chooses the president of the United States of America".

That message is in stark contrast to President Donald Trump whose campaign has pursued legal efforts to halt the vote counting in some states and is seeking a recount in Wisconsin.

Two days after voting day, an uneasy United States is still waiting to hear who will be its next president.

Biden is pushing closer to the 270 Electoral College votes needed for victory, with the decision resting on six key states.

The President spent the day at the White House, working the phones and escalating efforts to sow doubt about the outcome of the race. In a series of tweets, he pushed baseless allegations of electoral misconduct and said the ongoing vote count of ballots submitted before and on Election Day should cease.

Trump followed up with an all-caps official campaign statement. "IF YOU COUNT THE LEGAL VOTES, I EASILY WIN THE ELECTION! IF YOU COUNT THE ILLEGAL AND LATE VOTES, THEY CAN STEAL THE ELECTION FROM US!" he contended.

Biden's victories in Michigan and Wisconsin put him in a commanding position, but Trump showed no sign of giving up.

It could take several more days for the vote count to conclude and a clear winner emerges.

With millions of ballots yet to be tabulated, Biden already had received more than 72 million votes, the most in history. Trump's campaign engaged in a flurry of legal activity to try to improve the Republican President's chances, requesting a recount in Wisconsin and filing lawsuits in Pennsylvania, Michigan and Georgia.

Statewide recounts in Wisconsin have historically changed the vote tally by only a few hundred votes; Biden led by more than 20,000 ballots out of nearly 3.3 million counted.

Judges in Georgia and Michigan quickly dismissed Trump campaign lawsuits.

Biden has already won Michigan and Wisconsin. The contests in Georgia and Pennsylvania, along with Nevada and North Carolina, were tight with votes still being tabulated.

The Trump campaign said it was confident the President would ultimately pull out a victory in Arizona, where votes were also still being counted, including in Maricopa County, the state's most populous area.

Trump's legal challenges faced long odds. He would have to win multiple suits in multiple states in order to stop vote counts, since more than one state was undeclared.

There were no obvious grounds for the Justice Department to attempt to intervene to stop a vote count at the state level, unless the federal government could somehow assert a violation of federal voting laws or the Constitution.

The department could theoretically file a brief in support of a Trump campaign lawsuit if it believed there were federal concerns at stake, but that intervention would be extraordinary.

While Trump has insisted that ballot counting stop, it was unclear exactly what that included. Counting for votes received by November 3 was continuing, but roughly 20 states allow ballots to be counted if postmarked by November 3 but received in the days after.

In some states that is as long as nine days, or even longer. Some of the deadline changes were made as a result of the pandemic, but others are just routine parts of state election laws.

Trump has fixated on Pennsylvania, where the Supreme Court refused to stop a court's ruling that allowed for a three-day extension. He also said he was taking fraud claims to court – but most of the lawsuits only demand better access for campaign observers to locations where ballots are being processed and counted.

A judge in Georgia dismissed the campaign's suit there less than 12 hours after it was filed. And a Michigan judge dismissed a Trump lawsuit over whether enough GOP challengers had access to handling of absentee ballots. Biden attorney Bob Bauer said the suits were legally "meritless."

Their only purpose, he said "is to create an opportunity for them to message falsely about what's taking place in the electoral process".

Earlier, Trump saw his lead in Pennsylvania narrow to around 115,000 votes from around 600,000 in just 48 hours. Mail-in ballots in the state are heavily favouring Biden, as pollsters predicted.

Protests have broken out in various states, demanding either all votes be counted or the voting to stop immediately.

Dozens of Trump supporters chanting "Stop the count!" descended on a ballot-tallying centre in Detroit, while thousands of anti-Trump protesters demanding a complete vote count took to the streets in cities across the US.

Protests — sometimes about the election, sometimes about racial inequality — took place Wednesday in at least a half-dozen cities, including Los Angeles, Seattle, Houston, Pittsburgh, Minneapolis and San Diego.

Biden's victories in the Great Lakes states left him at 264, meaning he was one battleground state away — any would do — from becoming president-elect.

A result in the southern state of Georgia is due within hours where less than 20,000 votes separate Trump from Biden.

The President is leading in the state, however, Biden has been eating into his margin, taking it from more than 60,000 to less than 20,000 overnight.

It is a collapse similar to that which Trump experienced in Pennsylvania, where he led by 700,000 votes and is now in danger of losing the state to Biden — and the entire election along with it.

As reported earlier, the incumbent President's lead plummeted by 40,000 votes in Georgia in a single dump.

The President's team has admitted that Georgia is the make or break state. An adviser told CNN the state was "the difference between the White House and the outhouse".

If Biden wins in Georgia, he will be the first Democrat to do so since 1992.

For four years, Democrats have been haunted by the crumbling of the blue wall, the trio of Great Lakes states — Michigan, Wisconsin and Pennsylvania — that their candidates had been able to count on every four years. But Trump's populist appeal struck a chord with white working-class voters and he captured all three in 2016 by a combined total of just 77,000 votes.

The candidates waged a fierce fight for the states this year, with Biden's everyman political persona resonating in blue-collar towns while his campaign also pushed to increase turnout among Black voters in cities like Detroit and Milwaukee.

It was unclear when a national winner would be determined after a long, bitter campaign dominated by the coronavirus and its effects on Americans and the national economy. But even as Biden's prospects improved, the US on Wednesday set another record for daily confirmed coronavirus cases as several states posted all-time highs. The pandemic has killed more than 233,000 people in the United States.

Beyond the presidency, Democrats had hoped the election would allow the party to reclaim the Senate and pad its majority in the House. But while the voting scrambled seats in the House and Senate, it ultimately left Congress much like it began — deeply divided.

The candidates spent months pressing dramatically different visions for the nation's future, including on racial justice, and voters responded in huge numbers, with more than 100 million people casting votes ahead of Election Day.